With the exception of A166, the depths of the \(^{12}\) C\(^{18}\) O absorption bands in the dLHdC stars are comparable to those of the \(^{12}\) C\(^{16}\) O bands (see Figure REF ). From comparisons to synthetic spectra and using temperatures from Crawford et al. 2022 (in prep), we derive \(^{16}\) O/\(^{18}\) O ratios in the ranges 0.05–0.2 for B42, C38 and B566, 0.1–0.5 for A223, HD 182040 and HD 137613. Our derived values for HD 137613 and HD 182040 are consistent with those reported by [1]} from medium resolution and [2]} from high resolution spectra.
